Project Summary Given its central role in animal health and survival, the gut has evolved a sophisticated network of regulatory inputs from a variety of sources, including immunological, metabolic and microbiotic. Playing a prominent role in this regulatory network is the brain-gut axis, the bi-directional communication between the nervous system and the gut. While there are several well-described brain-gut signals, the exact mechanisms are not always well understood, and many of the signals, particularly stress signals and those involving the microbiome, remain elusive. The fruit fly Drosophila has emerged as a robust model system for unraveling the genetic and cellular basis of human disease, from cancer and neurological disorders to obesity and diabetes. This project seeks to develop Drosophila as a model system to study brain-gut interaction. A novel signal from the fly brain to the gut has been discovered that is activated by metabolic stresses such as fasting. Short Neuropeptide F (sNPF), a relative of mammalian Neuropeptide Y (NPY), is involved in this brain-gut signal. Preliminary studies suggest a model in which sNPF is secreted by a specific set of neurons that integrate the stress signal and innervate the gut. The sNPF signal functions to maintain heightened gut epithelial integrity during periods of stress; in its absence the gut loses epithelial integrity, resulting in an unchecked inflammatory response that depletes energy stores, leading to acute starvation sensitivity and shortened lifespan. The sNPF neurons that innervate the gut will be identified and specifically inactivated using the advanced genetic tools available in Drosophila. If the brain-gut stress signaling model is correct, inactivation of the sNPF neurons should result in the loss of epithelial integrity, inflammatory response and depletion of energy stores. Similarly, activation of the sNPF neurons should lead to enhanced epithelial integrity and resistance to bacterial challenge, and increased energy stores. The model also predicts that sNPF acts directly on the gut via its receptor, sNPF-R. To test this, sNPF-R levels will be knocked down specifically in the gut by RNAi and mutations in the sNPF-R gene will be generated. The discovery and verification of such a brain-gut signal will establish Drosophila as a genetic model system for brain-gut signaling during periods of stress and lay the foundation for identifying novel mechanisms underlying mammalian brain-gut signaling.